Local axis of imported objects
At the time of import: use the FBX options, and scale to 0.005 or 0.05
Else: Make an empty, import your 500 objects. When they come to scene make sure you are looking at your empty. then "A" (to select all), then "A" (or ALT+A if 2.8) and every object is now selected. LASTLY: SELECT YOUR EMPTY. Then hit CTRL+P (Parent objects), KEEP CURRENT TRANSFORMS.
Everything will be child of the empty object you made. Now, press "N" to bring the numeric panel on your 3D viewport. And try scale 0.05 on all X, Y, Z
See if that works.

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BFCT_Schiller